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Principles of Instrumental Analysis, 6th ed. Chapter 6
 
 2
 (j) Phosphorescence is a type of emission brought about by irradiating a molecular 
system with electromagnetic radiation. Phosphorescence involves a triplet-to-singlet 
transition and the excited state lifetime is longer than that of a fluorescing species. 
 (k) Resonance fluorescence is a type of emission in which the radiation produced is 
of the same wavelength as that used to excite the fluorescence. 
 (l) A photon is a bundle or particle of radiant energy with a magnitude of hν, where h 
is Planck’s constant and ν is the frequency of the radiation. 
 (m) Absorptivity a is defined by the equation a = A/bc, where A is the absorbance of a 
medium contained in a cell length of b and concentration c. The path length b is 
expressed in cm or another specifice unit of length. The concentration is expressed in 
units such as g/L. 
 (n) The wavenumber of radiation is the reciprocal of the wavelength in centimeters. 
 (o) Relaxation is a process whereby an excited species loses energy and returns to a 
lower energy state. 
 (p) The Stokes shift is the difference in wavelength between the incident radiation 
and the wavelength of fluorescence or scattering. 
6-2. 
10
17
8
2.998 10 cm/s = = = 4.80 10 Hz
6.24 Å 10 cm/Å
cν
λ −
×
×
×
 
 E = hν = 6.626 × 10–34 J s × 4.80 × 1017 s–1 = 3.18 × 10–16 J 
 E = 3.18 × 10–16 J × 6.242 × 1018 s–1 = 1.99 × 103 ev 
6-3. 
10
13 1
4
2.998 10 cm/s = = = 8.524 10 s
3.517 μm 10 cm/μm
cν
λ
−
−
×
×
×